Carburetor



Jan. 2, 1934. R F BRACK 1,942,199

CARBURETGR Filed March 2U, 1931 yPatented Jan. l2,A 1934 ,A VI'c.mnunuurl't)n. AImbert Fpracke, Chicago, Ill.; assigner,r by

meme assignments," to

-Lynn A. Williams,

Evanston, nl., ma cunard. c. nmlbury. Glencoe, Ill., successor t Appuomnn'mrcn 2o, 1931. c sel-1n a' 524,015? claim.. (c1. zei-o) My invention relates to improvements in carburetors and particularly carburetors of the fuel lift type wherein the `main fuel supply .tank is normally located below the level of the carburetor 5 and the carburetor arranged to produce a suction or depression for purposes of lifting the fuel from the lowlevel up to the carburetor.

One of the objects ofthe present invention is the provision of means for'providing a; fuel lift 1 carburetor made up of simple and inexpensive parts so arranged as to eliminate the necessity of extreme accuracy and'careful calibration.

A further object of this invention resides in the provision of an arrangement of parts whereby fuel metering of the carburetor is accomplished by a differential .in gravity head and an orifice andv entirely independently ofthe suction produced in the mixing chamber of the carburetor.

Afurther object of the present invention resides in the provision of improved means for reg ulating simultaneously proper proportions of air and fuel delivered by the carburetor.

These and other objects and features of this invention will be pointed out more clearly in con- V tending transversely through the mixingcham-- ber 3. The various parts above enumerated are not distinctly defined or shown in the accom.

panying drawing but it is to be understood that such parts will be so constructed that the assembly of the same may be madein the most o advantageous manner. It is to be also understood that the construction and flnal form of such parts will depend upon whether such parts are die-casted, sand molded or by other similar methods.

The secondary air intake port 5 is controlled by an air valve 26 arranged for longitudinal movement in the bearing 27. l This bearing is screw threaded in the housing 2 and has a knurled finger piece 8 arranged for cooperation' with a spring detent 9 suitably attached to the carburetor body. interposed between the bearing member 2'7 and air valve 26 is a compression spring 10 arranged to hold the valve 26 normally in its closed position as illustrated in the drawing.- The screw thread arrangement between the The carburetor is arranged to provide the.v

`in the drawing bearing 2'7 and the casing makes it possible to adjust the bearing up or down to provide the proper tension on the air valve spring 10. f

The air valve '26 has a hole l1 through which extends the pin 12 rigidly attached to the car-I 60 buretor casing, the purpose of this construction being to prevent any rotary movement of the air valve. Attached to the air valve is an arm 13 which has its outer end pivoted at 1'4 to a. metering pin 15 extending downwardly and. cooperating 05 with a seat 16 formed in the nozzle or'jet 17.- This jet extends upwardly into thethroat of the primary air intake 6 which as shown in the draw-1 ing, is formed to provide a venturi affording communication between atmosphere and the mixing chamber of the carburetor. The lower end of the nozzle or jet 17 has communication with the bottom of the oat chamber 4 through the duct 18.

The float chamber is madev air tight, or .practically so, and ca'rries the conventional float 19 15 and float valve 20 cooperating with the seat 21 in the fuel intake port 22. This fuel intake porthas communication with the low level supply tank 23 through the pipe 24.

Communicating with the float chamber 4 and so above the normal level of the fuel therein is a duct 25 the lower end of which communicates v with the throat of the venturi 6 at a point adjacent the upper end of the nozzle l17. As shown the float chamber 4 is located above the discharge end of the nozzle 17 so that a constant gravity head is provided between the level of the fuel in the float chamber and the discharge end of the nozzle. The amount of fuel discharged by the jet 17 is dependent upon this head and .the size of the orifice provided betweenl the metering pin 15 and the seat 16 of the nozzle. As the metering pin 15 vis connected with the air valve and arranged to move therewith the size of this orifice is regulated by the air valve and varies according to the taper provided on the metering pin and the position assumed by the air valve.

'Ihe operation of the device is as follows. Assuming that the motor to which the carburetor 100 is attached is operating, air is drawn into the carburetor through the primary intake port 6 and through the mixing chamber into the manifold of the motor. This flow of air causes the air valve 26 to move upwardly and assume a cer- 105 tain position depending upon the amount of air drawn into and through the carburetor. The air valve movement results in an upward movement of the'metering pin 15 to provide at "'16 the proper size orifice for delivering the proper Il() amount of fuel for the air admitted to the carburetor. In the operation as just described the mixing chamber 3 is placed under a reduction of pressure which results in a high velocity air ow through the primary venturi 6. This action in the venturi produces ahigh suction at the throat thereof and this high suction is communicated to both the jet 17 and the duct 25. The high Venturi suction is thus communicated to both the fuel in the float chamber and the air space above the fuel level in the float chamber. This highsuction is for the purpose of lifting the fuel from the low level supply tank 23 up into the carburetor. y

When the motor stops, the air valve 26 closes the metering pin 15 against its seat in the nozzle 17 to prevent leakage from the oat chambers.

From the above description it will be observed that the amount "of fuel delivered to the carburetor is entirely independent of the suction produced at the throat of the venturi 6. 'Ihe Venturi action of the venturi may vary considerably throughout the range of the motor without in anywayaifectingthe operation of the carburetor. In so far as fuel lift is concerned it is necessary only that the venturi produce sufficient suction at all engine speeds for lifting the fuel from lthe supply tank to the float bowl. v

In somewhat similar prior designs of fuel lift carburetors the float chamber has been at the level of the nozzle. There then being no head of fuel. A ow of the fuel has been produced by insuring that the air pressure on the liquid level in the float chamber was less than the air pressure on the nozzle. In Patent 1,370,949 to-Milford G. Chandler this differential of air pressure is shown as attained by a duct from the top of the float chamber communicating with the Venturi tube somewhat posterior tothe location of the nozzleat the throat. The top of the float chamber thus communicates with the venturi at a region where the suction issomewhat less than that at the region of the nozzle. Thishowever requires more critical limits in designing and adjustment than where the flow of fuel is caused by a uniformly maintainable head, in the carburetor here shown. Another objection to reliance upon a duct communicating at a region of the venturi axially displaced. from the nozzle is that there is a lessening of the suction produced in a venturi as the amount of fuel being discharged thereinto by the nozzle increases. For this reason it is difficult to maintain a uniform "pull on the fuel through the nozzle for different rates of fuel feed. v

I claim: p

1. A fuellifting carburetor having a Venturi tube connstituting a primary air intake, a variably restricted secondary air intake, a fuel reservoir subject to fuel lifting suction, with its liquid level above the Ithroat; of the Venturi tube, a fuel passage leading from the reservoir below the fuel level to a nozzle in the throat of the Venturi tube, and a duct communicating between the reservoir above the fuel level 'and the Venturi tube at a point longitudinally thereof substantially opposite the fuel nozzle and a carburetor suction responsive valve in the passage for metering the fuel flow to the nozzle, said duct serving tol balance the suction on the fuel level with the suction on the nozzle whereby the fuel flows only under the pressure of its head.

2.v A fuel lifting carburetor having a Venturi tube constituting a primary air intake, ya variably restricted secondary air intake, a fuel reservoir subject to fuel lifting suction, with its liquid level above the throat of the Venturi tube, a fuel passage leading from the reservoir below the fuel level to a nozzle in the Venturi tube,

and a duct communicating between the reservoir labove the fuel level and the Venturi tube at a point longitudinally thereof substantially opposite the fuel nozzle and a carburetor suction re- 105 sponsive valve in the passage/for metering the fuel ilow to the nozzle, saidduct serving to balance the suction on the fue'l level with the suction on the nozzlel whereby the .fuel flows only under the pressure of its head.

3. A fuel lifting carburetor having a Venturi tube constituting a primary air intake, a secondary air intake, a spring seated valve operable variably to restrict the secondary air intake, a fuel reservoir subject to fuel lifting-suction, with 315 its liquid level above the throat of the Venturi tube, a metering pin operable to control thelflow of fuel from said nozzle, and a connection between said metering pin and spring seated valve for actuating said metering pin by movement 120 y of the said valve, a duct communicating between the reservoir above the fuel level and the Venturi tube at a point longitudinally thereof substantially opposite the fuel nozzle, said duct serving to balance the suction on the fuel level with the suction on the nozzle whereby the fuel flows only under the pressure of its head.

ROBERT F. BRACKE. 

